Desalination has gained importance as an alternative water source. Brine effluent is a sub-product of desalination and can have negative effects on marine ecosystems. Numerical modelling is a prediction tool useful for the design of discharge configurations and for environmental impact assessment. The models CORMIX, VISUAL PLUMES and VISJET can be used for simulating negatively buoyant jets arising from brine discharges. A detailed analysis of the major assumptions, capabilities, limitations and reliability of these models is presented. Some important conclusions and recommendations have been elucidated. In a companion paper [1], an exhaustive validation of these commercial tools is carried out against experimental data found in the literature, focusing on brine jets discharged into both stagnant and dynamic environments. These two papers represent global research of the state of the art and the degree of reliability of existing commercial tools, using the most reliable experimental data available, and provide useful information for the technical and scientific communities. As such, they aim to improve the design and modelling of brine discharges. The conclusions outlined in the paper will improve the quality of environmental impact assessments of desalination projects and reduce the uncertainty associated with the use of numerical models. (C) 2011 Elsevier B.V. All rights reserved.